The studies in this laboratory are basically involved with studies of the mechanics and pharmacology if isolated heart muscle, using the papillary muscle preparation. A detailed application for these laboratory projects is included in the CVRI renewal application and is available for review in that document. Briefly, there are six projects which will be undertaken in this new laboratory. 1. The effects of hypoxia and inotropic interventions on the passive compliance (length- tension relation) of isolated cat papillary will be examined using a new constant lengthening technique. 2. The contractile function of cardiac muscle from the hypertrophied hearts of cats following an exercise program will be analyzed to determine potential differences in the contractability of muscle hypertrophied by exercise as compared to msucle hypertrophied by pulmonary artery constriction. 3. Pharmacologic studies will be performed to determine the potential role of alpha adrenergic receptors in mediating force development of ventricular myocardium. Preliminary studies suggest that alpha receptors are of importance in cat ventricle. 4. Combined electrophysiologic and mechanical studies of papillary muscles will be performed to determine the electrophysiologic correlates of afterload dependent and length dependent changes in contractile state. 5. Studies in the dog papillary muscle in vivo will be performed to determine if force and length dependent changes are present in a manner similar to isolated cat papillary muscle.6. A length controlled lever will be built in order to determine the active length-tension relation using length- tension loops at a constant contractile state and in order to evaluate the time independence of series elasticity.